Low-dose Sekikaic Acid Modulates Host Immunity and Protects Cells from Respiratory Syncytial Virus Infection

Abstract

Introduction: Investigations of Ramalina farinaceae and its isolated compounds had reportedly shown appreciable anti-RSV activity albeit within a slim therapeutic window. Sekikaic acid represent one of such compounds. In this present study, sekikaic acid in very low dose was evaluated  as a cell restorative and immunomodulatory factor. Methodology: The effect of sekikaic acid on the cell viability of RSV-infected HEp2 cells was investigated. Further assay for cellular immune response in primed mouse splenocytes was established by cell culture and flow cytometry.  Splenocytes were treated with graded concentrations of sekikaic acid (6.25-25 µg/ml) and screened for their effect on the expression of IFNγ and IL-2 and T-lymphocytes markers CD4+ and CD8+ using intracellular cytokine staining and Fluorescence-activated cell sorting (FACS) analysis. Results: Results reveal that sekikaic acid protects RSV-infected Hep 2 cells from infection-induced cytopathology. Moreover, sekikaic acid displayed some degree of immune-regulatory activity in the primed mouse splenocytes increasing the proportion of CD8+/IFNγ+ (70.95-73.8%) and CD4+/ IFNγ+ (3.44-4.13%) T lymphocytes when compared to the cells in untreated controls 2.75% (CD4+) and 69.35% (CD8+) respectively. Interleukin-2 (IL-2) expression and signalling by T-Lymphocytes was selective but pronounced for CD4+ cells activation (sekikaic acid 2.67-3.6%, control 0.44%). Similar scenario was recorded for Intracellular IL-2 secretion by the T-lymphocytes. Conclusion: Low-dose sekikaic acid protects RSV infected cells and lead to immune lymphocytes proliferation. This recorded T-lymphocyte-specific immune-modulatory property may contribute to explain in part the dynamics associated with the overall antiviral effect of Sekikaic acid, and may also find relevance as a necessary cellular immune response precursor to infection-associated disease management.